title: Membrane interface probe protocol for contaminants in low-permeability zones.
abstract: Accurate characterization of contaminant mass in zones of low hydraulic conductivity (low k) is essential for site management because this difficult-to-treat mass can be a long-term secondary source. This study developed a protocol for the membrane interface probe (MIP) as a low-cost, rapid data-acquisition tool for qualitatively evaluating the location and relative distribution of mass in low-k zones. MIP operating parameters were varied systematically at high and low concentration locations at a contaminated site to evaluate the impact of the parameters on data quality relative to a detailed adjacent profile of soil concentrations. Evaluation of the relative location of maximum concentrations and the shape of the MIP vs. soil profiles led to a standard operating procedure (SOP) for the MIP to delineate contamination in low-k zones. This includes recommendations for: (1) preferred detector (ECD for low concentration zones, PID or ECD for higher concentration zones); (2) combining downlogged and uplogged data to reduce carryover; and (3) higher carrier gas flow rate in high concentration zones. Linear regression indicated scatter in all MIP-to-soil comparisons, including R(2) values using the SOP of 0.32 in the low concentration boring and 0.49 in the high concentration boring. In contrast, a control dataset with soil-to-soil correlations from borings 1-m apart exhibited an R(2) of ≥ 0.88, highlighting the uncertainty in predicting soil concentrations using MIP data. This study demonstrates that the MIP provides lower-precision contaminant distribution and heterogeneity data compared to more intensive high-resolution characterization methods. This is consistent with its use as a complementary screening tool.
authors.affiliation: G360 Centre for Applied Groundwater Research, University of Guelph, Guelph, Ontario, Canada, N1G 2W1.
authors.forename: David T
authors.initials: DT
authors.lastname: Adamson
authors.forename: Steven
authors.initials: S
authors.lastname: Chapman
authors.forename: Nicholas
authors.initials: N
authors.lastname: Mahler
authors.forename: Charles
authors.initials: C
authors.lastname: Newell
authors.forename: Beth
authors.initials: B
authors.lastname: Parker
authors.forename: Seth
authors.initials: S
authors.lastname: Pitkin
authors.forename: Michael
authors.initials: M
authors.lastname: Rossi
authors.forename: Mike
authors.initials: M
authors.lastname: Singletary
mesh_terms: D004784:Environmental Monitoring / Q000295:instrumentation*; D005431:Florida; D060587:Groundwater / Q000737:chemistry*; D006843:Hydrocarbons, Chlorinated / Q000032:analysis; D010539:Permeability; D012989:Soil Pollutants / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006843:Hydrocarbons, Chlorinated; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical